A thread wound golf ball is obtained by winding a thread rubber on a solid or liquid rubber center to form a thread rubber layer and coating the outside of the thread rubber layer with a cover material (e.g. ionomer, balata, etc.). As the solid rubber center, a vulcanized butadiene rubber has been used in the prior art, and it has a considerably high hardness and small compression strain. In the golf ball with such a center, a spin amount is large and a launch angle is small, so that it is disadvantageous in view of flying distance. Further, the golf ball turns too much when hit the ball to control easily, sometimes.
On the other hand, a liquid center has a large compression strain. In the golf ball with such a liquid center, the spin amount is small and launch angle is large, so that it is advantageous in view of flying distance in comparison with a conventional solid center. However, in case of the liquid center, there was a problem that the production process is complicated and, further, a liquid in the liquid center is splashed when the golf ball is cut by a cutter, which results in loss of eyesight.
The present inventors have found that, by using a solid rubber having a crosslinked structure containing an oily substance as the center of the thread wound golf ball, the spin amount is reduced and launch angle is increased under a proper initial velocity, thereby improving the flying distance in case of wood and iron shot with keeping good balance (Japanese Patent Application No. 4-149304). However, the oily substance of the center causes bleeding with time to penetrate into the thread rubber layer, which results in deterioration of impact resilience. Accordingly, performances of the golf ball could not be maintained.